As I am want to get carried away when excitement overtakes me, I'll go against what they are recommending for ball and patch, and suggest, due to the shallow rifling and 75" twist, I'd prefer a .710" ball and a .018" to .020" patch. You need some compression in the bottom of the grooves or the powder gasses will blow past, burn the patch and foul the bore excessively.

There are ticking & denim materials (8 ounce) that meet this criteria, just as in the .018" range, you can find heavier linen which will 'answer' well and perhaps the best. these are COMPRESSED measurements- take calipers with you to the fabric shop, linen, or 100% cotton only. If using caliper for measuring, squeeze the tines between fore finger and thumb - as tightly as you can - that gives a compressed measurement. Do not trust 'packaged' materials - they do not measure 'crushed'. I find OxYoke .018" to be only .015" thick - it's too thin. their .020" or .022" might be OK - I'd expect .003" to .005" thinner than they actually say. As I noted, I use .030" in my `14 bore with a .682" pure lead ball - how would THEY measure that? It is .025" in my mic - crushed by the round anvils- ratchet turned. My brother's mic measures .001" differently than mine and all 3 of my dial mics give .001" different readings incrementally. I use the medium for all my measuring with calipers. The differences are due to different ratchet spring strength in the mic and different anvil widths in the mics. It does not take much, to make a .001" difference in measurement.

The muzzle will need re-crowing, but that is simple - I can explain it and show demo pictures.
I'd say, buy it and let the gun begin.

Just remember, velocity follows closely with pressure. The biggest or greatest reason not to increase the charge in this rifle, will be loss of accuracy or too much recoil, not too much pressure.

The almost 1 1/4" round breech will be very strong - I'd suggest their modest suggested powder charge is reflected in the useless .010" patch they suggest, or them not liking the recoil. I think perhaps they fouled very badly.

You may find 120gr. or 125gr. gives you all the fun (recoil) you want, with a 530gr. ball. These should give about 1,200fps or so, maybe 1,300fps. If mine and loaded more tightly, as I am want to do with my own rifles, I'd probably hunt this for elk and moose in the 140gr. to 160gr. range, but that is me. Start low- I suggest 3 drams, which is 82gr., get to know her and go from there - let accuracy and clean shooting be your guide.

If mine and using soft lead balls of .715", I'd be using a .022" patch. I suggested easier loading combinations which should work just fine with moderate powder charges to about 130gr. or so.

Using 2f powder, this rifle should develop virtually the same pressure at 1,500fps as a .58 or .67 cal rifle or my .69 at the same speed. To get that in a .58, you would need only 120gr.2F, or perhaps 130gr. in the 16 bore. My own .69 (14 bore) used to give me that speed at 165gr. 2G in 1986 with the GOEX at that time and my barrel was 31" and 1 1/8" across the flats, thinner than this one. I used that load up until 3 years ago when I found the 200yard sight's impact was higher- 220yards, so I've dropped the 'big' moose load to 140gr. for a zero to the 200yard sight at 200yards. Impact is now the same as before, so I expect velocity is similar as well - 1,500fps to 1,550fps or thereabouts. Good speed, point blank range of 125yards and great killing power! The bore guns rule!

Enjoy!

Nice rifle - I am impressed.